A Hybrid Cascaded H-Bridge Converter for Poloidal Magnets of Tokamaks

The high-performance control of tokamak plasmas requires the poloidal magnet power supply (PS) to have a large current output at the 10-kA class, a current slew rate at the 1-kA/ms class, and as low ripple as possible in both voltage and current. This article presents a modular multilevel converter composed of two cascaded H-bridges, powered separately by electrolytic capacitors and supercapacitors (SCs). A controller that could take advantage of different capacitors is developed. Simulation and test are carried out on spherical tokamak SUNIST-2. The results show that it meets the above requirements well.